Antioxidants Don't Appear to Lessen Cardiovascular Risk Among High Risk Women

15/08/07 Women who have a higher risk of heart disease might not get any benefit from consuming vitamins C, E and beta carotene, either on their own in combination - the antioxidants do not lower their risk of experiencing a cardiovascular event, according to an article in this week's Archives of Internal Medicine (JAMA/Archives).

The article explains that harm to cells caused by exposure to oxygen (oxidative damage) may be a contributory factor in cardiovascular disease. The writers add that free radicals may harm artery linings, trigger blood clots and modify the way blood vessels function.

Nancy R. Cook, Sc.D., of Brigham & Women's Hospital and Harvard Medical School, Boston, and team wrote that "Antioxidants scavenge free radicals and limit the damage they can cause. Diets high in fruit and vegetable intake, and thus rich in such antioxidants, have been associated with reduced rates of coronary heart disease and stroke. Vitamins C and E and beta carotene are potential mediators of the apparent protective effect of a plant-based diet on cardiovascular disease."

The scientists tested the effects of these compounds in the Women's Antioxidant Cardiovascular study, which tracked 8,171 women over 40 (average age 60.6 years) from 1995-1996 through to 2005. All the women either had a history of cardiovascular disease or had at least three risk factors. They were randomly selected to receive 500 milligrams of ascorbic acid or a placebo each day, 600 international units of vitamin E or a placebo every two days, and 50 milligrams of beta carotene or a placebo every two days. During the ten-year period they were followed up for the occurrence of stroke, heart attack, bypass surgery or death.

1,450 women had at least one cardiovascular event - this included 274 heart attacks, 298 strokes, 889 bypass surgeries or angioplasties, and 395 cardiovascular deaths out of a total of 995 deaths.

The writers observed that "There was no overall effect of ascorbic acid, vitamin E or beta carotene on the primary combined end point or on the individual secondary outcomes of myocardial infarction, stroke, coronary revascularization or cardiovascular disease death. There were no significant interactions between agents for the primary end point, but those randomized to both active ascorbic acid and vitamin E experienced fewer strokes."

They detected no additional side effects among the women who took the active pills compared to those on a placebo, except for a slightly raised risk of stomach upset among the active beta carotene takers.

The writers concluded "Overall, we found no benefit on the primary combined end point for any of the antioxidant agents tested, alone or in combination. We also found no evidence for harm. While additional research into combinations of agents, particularly for stroke, may be of interest, widespread use of these individual agents for cardiovascular protection does not appear warranted."